This application claims priority to German Patent Application No. 102 01 988.6 filed Jan. 21, 2002, which application is herein expressly incorporated by reference.
The invention relates to a torque limiting coupling in a driveline of an agricultural implement. The torque limiting coupling prevents agricultural implements from being damaged or destroyed by overloading. The torque limiting coupling separates the drive from the agricultural implement in cases where the torque required to drive the agricultural implement exceeds a limit value and where the risk of damage to the implement is present. This can occur, for instance, if the agricultural implement stalls.
DE 30 34 606 A1 illustrates a torque limiting coupling with a coupling hub and a coupling sleeve which is rotatably arranged around a longitudinal axis. The coupling hub includes apertures which adjustably hold driving members that extend parallel to the longitudinal axis. The driving members, in a torque transmitting position, engage recesses which correspond to the apertures. A switching disk is axially loaded by a spring and supported against the driving members so that the driving members are held in the recesses. The switching disk is rotatable between a torque transmitting position and a freewheeling position. The switching disk is spring-loaded in the circumferential direction towards the torque transmitting position.
When a predetermined torque is exceeded, the driving members are axially pressed against the spring force of the spring out of the recesses. The driving members roll on a side face of the coupling sleeve and thus rotate the switching disk into its freewheeling position where the driving members engage recesses in the switching disk. In this position, the coupling hub, with respect to drive, is disconnected from the coupling sleeve. Thus, torque cannot be transmitted between the coupling hub and the coupling sleeve. Furthermore, the circumference of the switching disk includes a radially outwardly pointing switching cam. A switching tappet is adjustably arranged between a releasing position and a locking position. In the locking position, the switching tappet cooperates with the switching cam so that, when the torque limiting coupling rotates, the switching disk is transferred into its freewheeling position. Thus, this interrupts the transmission of torque. A returning cam on the coupling lug moves the switching tappet back into the releasing position after the switching disk has been rotated. A disadvantage of this embodiment is that, after the torque limiting coupling has been disconnected, the latter is automatically re-connected at low speeds since the switching disk is spring-loaded towards its torque transmitting position. In consequence, the torque limiting coupling is automatically re-connected in any event.
DE 28 53 293 C2 discloses a torque limiting coupling which operates on the same principle as the torque limiting coupling according to DE 30 34 606 A1. However, there is no switching tappet that cooperates with a switching cam on the switching disk to disconnect the torque limiting coupling. A spring-loaded locking ball is in a radially extending bore of the switching disk. The spring-loaded locking ball, in the freewheeling position of the switching disk, engages behind a stop and thus holds the switching disk in the freewheeling position. After the torque limiting coupling has been disconnected as a result of an overload, it is not re-connected automatically after a predetermined low speed has been reached. The torque limiting coupling has to be manually connected.
It is an object of the present invention to provide a torque limiting coupling that interrupts torque transmission when an overload occurs. The torque limiting coupling enables automatic re-connection when lower speeds are reached. Also, the torque limiting coupling enables emergency disconnection of the torque limiting coupling and prevents automatic re-connection.
In accordance with the invention, the torque limiting coupling, in particular in a driveline for driving agricultural implements, defines a longitudinal axis around which the torque limiting coupling is rotatably arranged. A coupling hub has circumferentially distributed apertures. Driving members are held parallel relative to the longitudinal axis so as to be adjustable in the apertures of the coupling hub. A coupling sleeve drives the coupling hub. The coupling sleeve has first recesses that correspond to the apertures. A switching disk is rotatably arranged, relative to the coupling hub, between a coupling position and an uncoupling position. The switching disk is loaded towards the coupling position by a circumferentially acting spring. An axially acting spring loads the switching disk towards the coupling hub. The switching disk is axially supported against the driving members. The driving members, for torque transmitting purposes, engage the first recesses of the coupling sleeve. If a predetermined torque limit is exceeded, the switching disk can be transferred from the coupling position into the uncoupling position by a rolling movement of the driving members. The switching disk has second recesses that correspond to the apertures. The second recesses are engaged by the driving members in the uncoupling position. A locking mechanism is adjustable between a locking position, where the switching disk, in its uncoupling position, is locked to prevent it from being rotated into the coupling position, and a disengaging position. A retainer is adjustable between a retaining position, where the locking mechanism is secured in its disengaging position against displaced into the locking position, and a releasing position. A detent pawl is displaceable between a neutral position and a disconnecting position. The detent pawl, in the disconnecting position, cooperates with a radially extending switching face of the switching disk. The detent pawl transfers the switching face from the coupling position into the uncoupling position. The detent pawl, in the disconnecting position, cooperates with a radially extending switching face of the retainer. The detent pawl transfers the retainer switching face from the releasing position into the retaining position.
The locking mechanism is not transferred into its locking position until the torque limiting coupling is disconnected by the detent pawl. If disconnection results from an overload, the locking mechanism remain in its disengaging position. Thus, this ensures that the torque limiting coupling is not automatically re-connected after the torque limiting coupling had been disconnected by the detent pawl. Automatic re-connection is possible only if disconnection results from an overload if a certain speed is not reached. For example, the detent pawl can be actuated in those cases where an emergency off-switch is actuated. In such a case, the driven masses can be braked and stopped by a separate braking device without the torque limiting coupling being automatically re-connected when the speed falls below a certain speed.
According to a first embodiment, the locking mechanism has at least one locking member which is adjustable in parallel to the longitudinal axis. The locking member, in the locking position, holds the switching disk and the coupling hub in a rotationally fast way relative to each other. The locking member may be a spring-loaded pin adjustably guided in a bore of the coupling hub. The bore extends parallel to the longitudinal axis. The pin, in the locking position, enters a bore in the switching disk.
The retainer may be a retaining disk. The retainer disk is rotatably adjustable around the longitudinal axis relative to the switching disk. The retainer disk has an aperture that is aligned with the bore of the switching disk in the releasing position. The aperture enables passage of the pin. The retainer disk, in the retaining position, covers the bore of the switching disk and prevents the pin from entering the bore.
According to a second embodiment, the locking mechanism has at least one locking member which is radially adjustable relative to the longitudinal axis. The locking mechanism, in the locking position, holds the switching disk and the coupling hub in a rotationally fast way relative to one another. The locking member may be a spring-loaded roller. The spring-loaded roller is adjustably guided in a first radial recess in an outer circumferential face of the coupling hub. In the locking position, the spring loaded roller enters a second radial recess in an inner circumferential face of the switching disk.
The retainer is preferably an annular retaining disk. The annular retaining disk is rotatably adjustable relative to the switching disk, around the longitudinal axis. The annular retaining disk has a third radial recess which starts from an inner circumferential face. In the releasing position, the third radial recess and second radial recess are aligned with one another. Thus, the roller may enter both the second radial recess and the third radial recess. In the retaining position, the second radial recess and the third radial recess are arranged so as to be offset relative to one another. Thus, the roller is prevented from entering the second radial recess.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.